Isolate unreadable marker fixtures across target frameworks

TESTING_GUIDE.md

@@ -765,6 +765,7 @@ Use the inventory below before adding or moving a test class:
 - Separate pure `ProcessStartInfo` construction contracts from subprocess-environment filtering tests; only the latter mutate the parent process environment and require the non-parallel collection.
 - Keep freshness diagnostic classification parallel; isolate only the stamped-case probe test that temporarily replaces `GitHelper` and `FileIndexer` test hooks.
 - Production source-policy scans for direct environment access are read-only and parallel-safe; isolate the separate `CdidxEnvironment` mutation contract that changes a real process variable.
+- Fixtures that intentionally make a directory unreadable must own a unique `TestProjectHelper.CreateTempProject(...)` workspace outside the repository and test output trees. Default multi-target runs can execute target frameworks concurrently, so placing such a fixture under `bin` or `obj` can break another target's read-only source-policy scan before build-output filtering is applied (#5019).
 - Dependency-boundary source audits are also read-only and parallel-safe. Keep the CLI command metadata and config-source resolution assertions in the ordinary collection so changes that reconnect rendering, command routing, config loading, and environment access fail without adding process-global test state.
 - The reflection-only SQLite collection registration contract is parallel-safe; keep only fixture lifecycle tests that replace the global pool-clear callback in the sensitive collection.
 - Isolate config CLI cases that change current directory or real environment variables; ordinary config parsing and validation uses injected environment readers and independent temporary roots, so the main suite remains parallelizable.
@@ -1718,6 +1719,7 @@ dotnet test --filter "FullyQualifiedName~GitHelperTests"
 - pure な `ProcessStartInfo` construction contract と subprocess environment filtering test を分離する。parent process environment を変更して non-parallel collection が必要なのは後者だけである。
 - freshness diagnostic classification は parallel 実行し、`GitHelper` / `FileIndexer` test hook を一時的に置き換える stamped-case probe test だけを隔離する。
 - production source の direct environment access policy scan は read-only で parallel-safe である。実 process variable を変更する別の `CdidxEnvironment` mutation contract だけを隔離する。
+- directory を意図的に unreadable にする fixture は、repository と test output tree の外側にある一意な `TestProjectHelper.CreateTempProject(...)` workspace を所有する。default の multi-target 実行では target framework が並列に動くため、この種の fixture を `bin` / `obj` 配下に置くと、build-output filter が適用される前に別 target の read-only source-policy scan を失敗させる可能性がある (#5019)。
 - dependency boundary の source audit も read-only で parallel-safe である。CLI command metadata と config-source resolution の assertion は通常の collection に置き、rendering、command routing、config loading、environment access を再接続する変更が process-global test state を追加せず失敗するようにする。
 - reflection だけを行う SQLite collection registration contract は parallel-safe である。global pool-clear callback を置き換える fixture lifecycle test だけを sensitive collection に残す。
 - current directory または実 environment variable を変更する config CLI case を隔離する。通常の config parse / validation は注入された environment reader と独立 temporary root を使うため、main suite は parallel 実行可能に保つ。

changelog.d/unreleased/5019.internal.md

@@ -0,0 +1,16 @@
+---
+category: internal
+issues:
+  - 5019
+affected:
+  - tests/CodeIndex.Tests/McpServerToolsCallTests.cs
+  - TESTING_GUIDE.md
+---
+
+## English
+
+- **Unreadable marker fixtures no longer interfere with concurrent target-framework tests (#5019)** — the MCP marker-fingerprint fixture now uses an isolated temporary workspace outside repository build outputs, so a source-policy scan in another target framework cannot recurse into its intentionally unreadable directory.
+
+## 日本語
+
+- **読取不能な marker fixture が target framework 間の並列テストへ干渉しないようになりました (#5019)** — MCP の marker-fingerprint fixture を repository の build output 外にある独立した一時 workspace へ移し、別 target framework の source-policy scan が意図的に unreadable にした directory へ再帰進入しないようにしました。

tests/CodeIndex.Tests/McpServerToolsCallTests.cs

@@ -13407,10 +13407,10 @@ public void ToolsCall_Index_Rebuild_IgnoresUnreadableDirectoriesWhenCollectingMa
         if (OperatingSystem.IsWindows())
             return;
 
-        var fixtureDir = Path.Combine(Path.GetFullPath("."), $"mcp_index_unreadable_marker_{Guid.NewGuid():N}");
-        Directory.CreateDirectory(fixtureDir);
+        var fixtureDir = TestProjectHelper.CreateTempProject("mcp_index_unreadable_marker");
         var dbPath = TestProjectHelper.CreateTempDbPath("cdidx_mcp_index_unreadable_marker");
         var unreadableDir = Path.Combine(fixtureDir, "secret");
+        var originalCurrentDirectory = Environment.CurrentDirectory;
         UnixFileMode? originalMode = null;
         try
         {
@@ -13421,6 +13421,7 @@ public void ToolsCall_Index_Rebuild_IgnoresUnreadableDirectoriesWhenCollectingMa
             originalMode = File.GetUnixFileMode(unreadableDir);
             File.SetUnixFileMode(unreadableDir, UnixFileMode.None);
 
+            Environment.CurrentDirectory = fixtureDir;
             using var server = new McpServer(dbPath, ConsoleUi.LoadVersion());
             var request = new JsonObject
             {
@@ -13444,6 +13445,7 @@ public void ToolsCall_Index_Rebuild_IgnoresUnreadableDirectoriesWhenCollectingMa
         }
         finally
         {
+            Environment.CurrentDirectory = originalCurrentDirectory;
             if (originalMode.HasValue && Directory.Exists(unreadableDir))
                 File.SetUnixFileMode(unreadableDir, originalMode.Value);
             TestProjectHelper.DeleteSqliteDatabaseFiles(dbPath);